Multiplex telegraph system



Aug. 3 1926.

H. H. HARRISON MULTIPLEX TELEGRAPH SYSTEM Filed May 21. 1924 2 Sheets-Sheet 1 HG. 5. pm

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Patented 3, 192.6. y UNITED' Asix'fxr PATENT omer...

' e. y l HARRY HUGHES HARRISON, OF LIVERPOOL, ENGLAND, ASSIGNOR T0 AUTOMATIC TELEPHONE MANUFACTURING COMPANY, LIMITED, 0F LIVERPOOL, ENGLAND.

, MLTIPLEX TELEGRAPH SYSTEM.

Application flled IIay 21, 1924, Serial No.f 714,921, and in Great Britain August l0, 1928-.

The present invention relates to multiplex telegraph systems andhas for its object the extension of the number of channels normally in use by the provision of an arrangement whereby the normal number of channels available in' anequal letter system suchas five unit code of the Baudot system may be increased without any sacrifice of line time. this is eiected b applying the two-power method of .signa ling, such as is employed in the/Morse quadruplex system, to an equal letter` system, employing for instance the tive unit code of the Baudet system. e

The two-power method 'as employed in the Morse quadruplex system consists essen;`

tially of superimposing two setsof signals,

one being double current signals operating a of highly complicated and expensive appa-A polarized relay while the other set are single current signals of augmented strength op-` erating a non-polarized relay which is marginally adjusted so `as not to operate with the weaker signals of the first set. This system is unsatisfactory in. that unless special measures are taken which involve. the use Ratus, signal elements occurring in the two j sets of signals will not in general commence at` the same instant and hence it will frequently occur that the single current (augmented power) signals will be reversed during a signal'owingV to the action of the double current signals,` If -such a reversal takes place, during; tone of the augmented signals the non-polarized relay w1ll momentarilyl release, the signal will be split, and there Will be a tendency to produce distortion.

v Various devices have been used for bridgf ing this interval of no current but they all `have the defect of slightl lengthening the 4faugmented signals since-t eyoperate when these signals cease as well as when a reversal, 1 takes place during the signal. Furthermore the presence of this n'o. current point fixes a power Morse quadruplex operation 'is poslimit to the length of line over. which twosible, since it is necessary to ensure that when the currentis reversed the .change in sign shall be asrapid as possible... This I makes it 'desirable'to have "a high voltage for the augmented signals, say two or three times as eat as that of the doublecurrent signals.

is very susceptible to interruption owing to the circuits becoming out of balance, .for out According to the present invention" Culty nals alone cause serious interference when augmented signals are being transmitted as well, andthe double current channel may very soon become unworkable.

.According tothe present invention, by the application of the two-power method-of working to the Baudot system, the signalling elements in Iboth sets of vsignals commence and terminate together and consequently there can be no splitting in the augmented signals since nov` current reversal occurs during their transmission.. On this account the augmented voltage maybe reduced very considerably and the danger of failure from balance variations' is very much reduced. Consequently one of. the most serious drawbacks of the two-power method of working is overcome and no undue restriction is placed on the lengthI of the line.

A preferred form of carrying the invention into effect will now be considered with f reference tothe accompanying drawings, although it will be understood that various modifications could be made to the arrangements described without departing from the spirit of the invention. v

Fig. l1 of the drawings illustrates the diiworkingof the two current system.

dinates current and it will be seen that the signal Z is being sent over the double current channel and the signal f overr the single current augmented power channel. With the phase relationshi of thetwo sets of signals as shown, it wi be observed thatiat the pointsmarked with a cross the sign @of the augmentedl power signals is reversed'l and the'relay operated by them will therefore momentarily release. If, inorder to over come this defect, means are introduced for mentioned 'with Morse quadruplex In Fig.' 1, abscissae represent time and or- I bridging this interval 'as mentioned above, 7

these means will also come into operation at vthe points y thus lengtheningthe signal Two embodiments of the invention now be described, these being illustrated 1n Figs. 2 and 3.

Figf 2 shows p to the sending of two sets of slgnals. simultaneousl'ypfrom stationA to stationv l, apparatus being shown for this directlon of how theinv'entionl is applied working only, though the line is assumedv 11 to be duplexed. Rotary distributors TD and RD are provided at the transmittin and receiving ends respectively and anyo the usual means well known in the art may be employed for securing that these rotate in synchronism. The -solid ring of each distributor is connected to earth and thus the tive contact segments corresponding to the ve @elements of the code are connected toearth lll ' tact of the transmitter TR1 is operated, a cir- -from battery cuit will be completed `for the relay `R1 which will connect up the battery BR to the line L in place of the battery BB1. Similar results will be produced by'other operated contacts of the transmitter TR1 as thebrushes continue to rotate and thus signals are sent out on the two current system which represents normal working. If any of the contacts of the transmitter TR2 had been operated however, when the brushes arrived at the appropriate contact, a circuit would be completed for relay R2. This then operates to short circuit the series resistance SR cand to remove the leak to earth LR, this being a well-known arrangement for increasing thel current in quadruplex working. Alterna-` tively also Rzcould be arranged to 'insert SR and connect up LR thus decreasing the current. l f

At the receiving station B the line extends through the non-polarized marginal relay 4NPR and the olarized relay PR in series, the branch lead from PR extending to the transmitter at the station B for working in the other direction. The relay PR is of the type normally fused and`is operated in. one dlrection by current of onepolarity and 1s restored by current of opposite polarity.

The relay NPR has; a biased armature and is only operated by currents .of increased strength but of either Apolarity and is restore to normal as soon as such currents` cease to flow.

The relay PR is adapted to complete circults for a group of 'rinting magnets PMG-,

B and) to earth by wa of the Solid ring of the distributon RD,-W ile'the relay NPR similarly controls a group of printing magnets PMG1. Other types of re- PR will take ceiving a lp'aratus could clearly bev employed rf desire It will then be seen that for each contact of the transmitter TR1 that is operated, a corresponding operationof the relay place and hence the corre-l `spending z printing magnet in the group PMG will be operated also. vSimilarly the p printngmagnetsof the group PMG*1 are Y.operated corresponding to the operated conof the receiving distributor RD1.

la)7 PR1 however in thls case-does not control` parent to those versed in the' art.

Referring now to Fig. 3 this shows a slight modification of the previous arrangement whereby one set of signals may be made to operate receiving apparatus while the other set is retransmitted over a line not employing the method of two power signalling.

Only the apparatus at the receiving end is shown, that at the transmitting end being similar to that shown in Fig. 2. Signals coming over the line' L1 traverse the nonpolarized relay NPR1 andthe polarized rea'y PR1 in series, the lead from PR1 extendy ing as before to the transmitters for working in the other direction. The relay NPR1 controls the operation of the group of printing magnets PMGr3 ,as before by way of the solid ring, brushes and contact selglilnents e reany printingmagnets but repeats vordinary double current signals over a further outgoing line L2.

It will of course be necessary in this case that the receiving distributor at the incoming end of the lin e L2 shall rotate' in s nchronism with the original transmit-ting istributor at the other end of the line L1.

It will thus be appreciated that by means ofthe present invention any of the channels of a Baudot system! may be supplemented by the use of a two-power method of working thereover, so that While theline time may normally be lfully utilized, additional channels' may be made available as and when required without materially affecting the apparatus vin use. This arrangement therefore doubles the capacityof any five unit system such as that of Baudot and en ables forked andyechelon working to be developed lto a greater extent thanordinarily.

What I claim isz- 1. A multiplex telegraph system comprisl ing a line, a rotary distributor at the transmitting end of said line, a second rota distributor at the receiving end 'of sai line adapted to rotate in synchronism with said first distributor, means controlled by said first mentioned distributor for causing currents to flow oversaid line whichma Adiffer inA polarity according to Aone signa to be transmitted, and means also controlled by said first mentioned distributor for causing 4the currents flowing over said line to be vaing in combination a telegrap line, two sets sistem compris- I for sending a current having a particular' characteristic, over said line under the control of said distributing switch, means controlled by the other set of transmitting means for sending a current having a characteristic distinct from said first current over said line'under the control of said distributing switch simultaneously with the transmission controlled by said first means, a second distributing switch 'at the receiving end of said line, and two sets of responding means connected to contacts of said switch and adapted to respond respectively under the control of said switch to the two distinctive currents transmitted so as to produce two separate records at said receiving end correspondin to the operation of said sets of transmittin means.

3. A multip ex telegraph system comprising in combination a set of transmitting keys having contacts connected to a distributing switch, a second set of transmitting keys connected to the same contacts of .said distributing switch, a telegraph line, a source of electrical energy, means controlled by said distributing switch and said first set of keys for altering the polarity of the current flowing over said line from said source, means controlled by said distributing switch and 'said second s et of transmitting keys for altering the strength of the current fiowing over said line, a polarized relay connected to the other end of said line for responding to said changes in polarity, a marginal relay also connected to the other end 4of said line for responding to said changes in strength, a second distributing switch located at the other end of said line and operated in synchronism with said t first distributing switch, a set of' recording apparatus controlled by said distributing switch and said polarized relay and a second set of recording apparatus controlled by said distributing switch and said marginal relay so that said first recording apparatus' responds to the operation of said first set of transmitting keys and said second recording apparatus responds to the operation of said second `set of transmitting keys.y

4. A multiplex telegraph system comprising in combination a telegraph line, two sets of transmitting means, a distributing switch to the saine contacts of which corresponding parts of both said sets are connected, means cont-rolled by one set of transmitting means for sending a current having a particular characteristic, over said line under the control of said distributingswitch, means controlled by the other set of transmitting means for sending a current having a characteristic distinct from said first current over said line under the control of said distributing switch simultaneously with the Ytransmission controlled by said first means,

a second distributing switch at the receiving end of said line, two sets of responding means connected to contacts of said switch and adapted to respond respectively under the control of said switch to the two distinctivev currents transmitted, a second telegraph line, means controlled by one of said responding means for re-transmitting a distinctive current over said second line, and means controlled by the other of said responding means for causing the signals responded to be recorded.

5. A multiplex telegraph system comprising in combination a telegraph line, a set of transmitting keys having cont-acts connected to a distributing switch, a second set of responding to said changes in strength, ay

second distributing switch located at the other end of said line and operated in synchronism with said first distributing switch, a set of recording apparatus controlled by said second distributin switch and said marginal relay, a secon telegraph line, a second source of electrical energy, and means controlled by said polarized relay for altering the polarity of the current flowing over sa1d second line from said second source.

In testimonyl whereof I aflix my signature.

HARRY HUGHES HARRISON. 

